The problem with translating the rest of this joke is that there is almost nothing that could make the rest of the puns make sense in English.
But I will make an attempt.
UPDATE: Butchered gratuitously for science. This is the worst pun I have ever had to make in the effort to not just write the Japanese words in romaji. You should've seen the ones I threw away for being too horrible.
Updated
Ah, I see, so that's how it is! I understand now!Chi-mat-a, Chi-mat-a done it now...!
"chimatta" by itself sort of means [verb] was done regrettably, accidentally, or as an unfortunate consequence of something elseH'aww~... Chi-mat-a (she might've) went and did it...!
"yacchimatta" - approx. "I goofed!/I did it, unfortunately!"H'AWW~...!Tenkyuu!!